SAFC With Cams

[cgg17]

Hello all,
I am having issues with my 95 Sl2 regaurding poor idle and rpm increases between shifts.
I am running reground twin intake cams, exhaust side rotated 180* and retarded 2 teeth. Prior to the regrinds I had stock twin intake cams (as well as a few other external bolt ons), and it ran well. After installing the regrinds, I have had an issue with horrible idle unless I lean out my SAFC to the maximum at the 800rpm setting. My wideband still is reading rich, which I assume is the PCM compensating for the false lean given by the overlap from the regrinds. What it will do is it will dip to about 500 rpm, stutter for 2-5 seconds, then go back to normal idle. Sometimes it catches itself, other times it stalls. If I have it leaned out all the way at the 800rpm setting, it will always catch itself but then it has a horribly lean tip in when accelerating from 800-2400, where the second setting is. I have that set richer than normal to help with the lean tip in. But that seems to be causing a jump in rpm's while shifting.
I am not too sure what to do, the only thing I can think of is I have too much overlap and the PCM is not thrilled about it?
Anybody have suggestions to try to either increase my idle speed or to help it catch itself when the rpm's drop? Or is it time for megasquirt?
Thanks,
Chris

[leighv]

3rd gen PCM worked OK with mild cams but the microsquirt seems to solve all issues with stock PCM. no real downside if you have the IAC controller

[cgg17]

3rd gen PCM worked OK with mild cams but the microsquirt seems to solve all issues with stock PCM. no real downside if you have the IAC controller

Microsquirt? Is that similar to megasquirt? I assume it is the same, but I have never heard of it. I am going to try to find a used megasquirt ms2 or newer over the summer to fix some of my issues.

[SC2Sick]

It's similar. All made by DIYAutotune I believe. I'd check out a TEC if you can get one though. importsdontlikeme

[cgg17]

It's similar. All made by DIYAutotune I believe. I'd check out a TEC if you can get one though. importsdontlikeme

I would get a TEC if I had the funds for that... Megasquirt seems to be more affordable and good enough for the job.

[SC2Sick]

I would get a TEC if I had the funds for that... Megasquirt seems to be more affordable and good enough for the job.

Make sure you get either a trigger wheel or the JBPerf VR conditioner then. Clean ignition signal with the native VR will be very, very frustrating.

[cgg17]

Make sure you get either a trigger wheel or the JBPerf VR conditioner then. Clean ignition signal with the native VR will be very, very frustrating.

Which is the most effective? Or which is better? I read that the trigger wheels are more precice but I would prefer to keep using the stock sensors.

[SC2Sick]

Which is the most effective? Or which is better? I read that the trigger wheels are more precice but I would prefer to keep using the stock sensors.

If you try and run the stock VR sensor without the signal conditioner on the board you'll probably have major crank signal issues. There are 2 pots on there you have to tune like an old VHF/UHF antenna and after hours of driving around I still couldn't dial it in right with those to even have clean enough crank signal to tune.

Once I installed the conditioner board in immediately had perfect signal.

http://www.jbperf.com/dual_VR/v2_1.html

[cgg17]

If you try and run the stock VR sensor without the signal conditioner on the board you'll probably have major crank signal issues. There are 2 pots on there you have to tune like an old VHF/UHF antenna and after hours of driving around I still couldn't dial it in right with those to even have clean enough crank signal to tune.

Once I installed the conditioner board in immediately had perfect signal.

http://www.jbperf.com/dual_VR/v2_1.html

That seems like a cheap price to pay for a clean signal...
I really don't know much about megasquirt, I plan on buying one if I can find a good deal on a used one or just buy a kit and assemble it myself. I've been reading on here and it seems the best thing to do is to make a whole new harness and drop it in with the squirt all as one. I'm also unsure about the fuel pump, I assume since I am OBD1 that the megasquirt doesn't touch the pump,since it is a return style system? I could be wrong but that is what I have gathered about that so far.

So really all I would need is the MS Board, Wire harness, and a VR Conditioner? As well as pigtails for all of the stock sensors.

[SC2Sick]

Yes. I recommend making a separate harness for your spark/fuel that way you can fall back to the stock PCM in a pinch. Run it in parallel.

I also used a 3G CPS extension harness to make an interceptor of sorts between the CPS and stock sensor plug for it. On the 3G they had to add a length to allow you to reach the sensor with the manifold in the way and it works great if you can find one. I was able to run shielded wire for the ignition signal all the way back to the MS that way. You can still run the tach and gauges on the dash doing it this way as well. You'll need to get a toggle switch for your fuel pump though if you're running fully off the MS or set it to a relay to trigger it.

[cgg17]

Yes. I recommend making a separate harness for your spark/fuel that way you can fall back to the stock PCM in a pinch. Run it in parallel.

I also used a 3G CPS extension harness to make an interceptor of sorts between the CPS and stock sensor plug for it. On the 3G they had to add a length to allow you to reach the sensor with the manifold in the way and it works great if you can find one. I was able to run shielded wire for the ignition signal all the way back to the MS that way. You can still run the tach and gauges on the dash doing it this way as well. You'll need to get a toggle switch for your fuel pump though if you're running fully off the MS or set it to a relay to trigger it.

I think I would go with a relay. Thanks for the CPS extension harness idea, I'll have to grab one this weekend. And I'm going wednesday to check out a 94 for parts, I may pull the whole engine harness so I have one to mess with, or at least one to see what pigtails I'll need to buy. I would prefer to buy them new and I know I can, they seem to be generic gm weatherpack.